Speedometer with rotating magnet



May 10, 1932. J z -ry 1,857,674

SPEEDOMETER WITH ROTATING MAGNET Original Filed Oct. 7, 1926 I I IIIIIIIIIIIIIII Patented May 10, 1932 JOSEPH ZUBATY, or FLINT, MICHIGAN,ASSiGNORQTo A. o sPA or FLINT, MICHIGAN, A COMPANY or vucniea v K rims; coMrAnY,

SPEEDOMETER wrrn aomwma amas M Application filed October 7, 1926, Serial No. 140,198. R enewed April 29, 19%. v

' This invention relates to measuring instruments, and more particularly has been designed as an improvement 1n a magnetic speedometer for vehicles. a V a 5 An object of the invention is to combine the advantages of different known types of instruments and to avoid their disadvantages; Another object is to employ comparatively M light rotating parts to thereby increase the life of the flexible drive shaft. 7

Another object is to so construct astraight bar magnet as to overcome the inherent dis advantages of its lesser efficiency as compared with instruments of the ring and horseshoe type. g

As another object, theinvention'contemplates such a relative position of parts as to take full advantage of all available'magnetic v, lines of force.

Among more incidental advantages are the provlslon of meansto prevent lnterference from outside sources, and to'afiord a very convenlent zero polnter.

Among the contemplated objects of the vent-ion, arealso, means which may be used with'the magnetic speedometer, having the above advantages, to act as a damper to prevent oscillations of the speed cup with sudden changes in speed; and the use of a temperature sensitive-means to correct errors arlsing' from changes in temperatures. a v

A reading of the following description and an examination of the accompanying drawings will make known the structure designed to secure the above enumerated and other 0bvious advantages of the invention. r 1

on a larger scale and showing the thermostatic control used with the magnet.

Figure5 isa plan view looking at the bottom of the 'magnetshown in Figure 4. 1

modified form showing the friction damper. Referring by reference characters to the drawings, and first to Figures 1 to 3 inclusive,

13. It is-preferably, a steel stampinge A numeral :lis a frame member whichis preferably a die casting.

The frame is to be positioned within a casing,not shown, andcarries a shaft 3 vertically journaledthereinp At-the lower end, shaft 3=is suitably constructed for connection with the driving shaft extending .to a point out i I end jofthe shaft is spun over at 15.- This magnet has the shape of astraight bar.- Part '8 is a stationary'armature of cup shape envelopingthe top, sidesandends ofmagnet plate 17 and fastening means 19 support the armature 8 onthe frame 1. Within the space between the armature 8 and themagnetisa speed cup or dragelement 2Q. Thespeedcup I is carriedon a rotating'b-e'aringl23 within the rotating shaft 3. -A ring -jewel25 is "also used abovebearing 23. ,Atits upperend the spindle 2111s guided bya stationary'bearing.

Zcafliedby the fixedarmature. Abovethe :e'nd fthe spindle is a suitable stop 26. to 'lim'it @81 ftheupwardmovement of the spindle.-

The magnet is not in the formof a single barbut is'in thefo'rm of a pluifality-of bars of similar dimensionssuperposed one upon' the other-to secure certain advantages'to'be l j eXplain'ed below; In the drawlngs, Figure 1 1s a vert1ca1 se Between the armature andthe speedcup is' a hair spring 27 secured at one endp'to-the spindle and at its other endto a lug 29 extending downwardly from'above] This spring is intendedto bias the cup to aposition where its zero is opposite a pointer'31, on a portion of the armature which-is cutaway-as shown at 33 to render visible theindicating. numerals on the speed cup, thesenumerals V a beingread through the usual openings in the Figure 6 is a vertical-section through a" dial plate 35 as shown in Figure EZ."

ln Figures 4; and 5 there is s'hown an ar rangement whereby automatically compen- SEL GIIIg means 1s provided to-correct for" errors in readings due to variations in temperature. Pole shoes 37 are provided on one or both, preferably both ends of the magnet. These shoes slide on the magnet and are guided by 5 rivets 39 carried by the ends of the magnet, which: rivets move in slots 41 in the shoes.

Theshoes have arms &3 proje'cting'upwardly along side the magnet, the arms aiding in guiding the movement of the shoes along the magnet. 4515a stamping of thermostatic metal, shaped as shown an'd secured to the-rotating shaft with the magnet. At each side of its centre attachme'nt'the thermostatic member is oftu-shape theouter ends-.of.-the. U being connected to the shoes as shown. The characteristics of the thermostat. are. such .that with an increase in temperaturethe shoesare movedoutvvardly along theends of the magnetltoward the speed cup and' armature. The air gap betweenethemagnet and-speed: cup is thus made variable and dependent upon changesiin temperature.

Inv Figure 6, is illustrated: an arrangement to prevent-undesirable oscillationsof the ro- EB tary. spindle andspeed cup.-.' The expedient isshown in a somewhat different relation but could as well be appliedinthe relation shown by Figure 1. In. Figurefithe plate 51 has an aperture to=receive a cup 53*, pressed into 910 theplatei' 5'1 and spunover at 55.. The cup is also serviceable as a pivotzfor a hair spring adjusting arm 57,.the-hair spring; being connected to the spindle and to a" part 59 projecting fromthe-arm. The-adjusting device 57 is' held in position by a generally-U-shaped spring: 61" straddling an adjusting screw 63 which: passes througlr a' forked end of. the spring. and into the plate 51. The" screw 63 engages its end the upper arm; of the spring and'its. adjustment varies theclearance at the-upperendof the spindlei Threaded to the cup"53-is a cover 64E havingaslotfor a screw driver to permit itsadjus-tment within the cup: A bearing 65-is positioned adjacent thebottomof the-cup 53 toguidethe spindle 21. Just. above the bearing is'a: stamping 67 having: extruded part 69.. Between the stamping: 67 and the cover 64 the space is filled with fine cotton to afford a desired degree" of friction upon the spindle, the extruded portion 69 guiding the spindle and keeping the lint from the cotton away from the bearing.

' In designing the speedometer having the structural characteristics above enumerated there-have been considered the relativemerits of the several known shapes of. magnets also there has been taken into consideration th'e advantages of the fixed and rotary type of magnet, both of course well known. In the revolving magnet of ring shape the 7 full strength of theimagnetv is not available becauseithelines-of forcein large measure cross theair gap between; the poles and do not intersect the drag element. To overcome this disadvantage, the magnet must be made heavier and larger which introduces a heavy strain upon the flexible drive shaft and re duces its life. Moreover. the ring shape in volves manufacturing clifliculty and requires 70 a grinding. operation to correct for deformation after heat treatment Compared with the ring and horseshoe magnets, a rotating bar magnet surround-ed a fixed cup shaped armature results not only in-alight and cheap arrangement but possesses very great effi ciency since practically all lines of force intersect thed'r'ag element. Furthermore, the light weightof the magnet lessens the strain upon the flexible drive shaft.' It has been found that the light rotating parts add greatly to'the life ofTthe flexible shaft. i

Although it istr-ue that (efficiency is .obe tained by a structure arranged so, that substantially all thenlines of forceintersect the speed cup,the inherent disadvantageof the bar magnet, as'compared with the magnet of ring and horseshoe type has notbeen-neglected. The bar magnet cannot: be sohighly magnetized and this is trueprobably because of the fact that in the ringand horseshoetype there'is but a small. air. gap through whichthe lines of forcemust pass, wh'ereasin: the bar type: of magnet, the gap may be said to be longer than the magnet itself.

To render the bar magnet as'efficient. as possible cognizance has been ta'kenof' the fact that to obtain the greatest eficiency in any magnet it is necessary to maintain a certain relation between its length and cross section. It is, therefore, not possible to increase the thicknessof a bar magnetzbeyond certain=limits in an attempt to increase its efliciency. Thisdisadvantage has been overcome 'by making the magnet of several component parts'each'of'whichpossesses a most desirable ration between its length and cross section. Three magnets each two inches long, inch wide, and A; inch thick will be found to be more powerful thana single magnet having the combined dimensions ofthe three.

Incidentally too, the thinner stock can be handled much more advantageously in stamping. Byniaking themagnets in this 5 way, the relative disadvantages of the bar type have been overcome.

The enveloping of the bar magnet lwithin steel cup possesses another advantage. The

instrument is not susceptible to outsideinterferences such asheavy steel partsorelectric wires. The magnet case for such an instrument may be made-of any desired material, magnetic or otherwise.

- he structurealready described provides for, a convenient arrangement of the zero pointer. When ithas been necessary toplace this pointeron the'dial and make it of a different color from the dial plate, difficulty has been encountered which will be avoided when One advantage of a stationary magnet and a speed cup rotatable between its poles-is the influence of the strong magnetic pull to 'prevent oscillations of the speed cup caused by sudden changes of speed. In the case of a rotating magnet this check upon the oscillations of the speed cupmay be had by friction in the spindle jewel bearing. This however makes the indicator slow at the start because a certain speed will be required to overcome the friction in the bearings before any moverotatable bar magnet, and an independent rotatable speed cup surrounding the same, a fixed armature enveloping said magnet and speed cup, a shoe of magnetic material" slidable upon an end of said magnet toward and from the armature, and heat sensitive means to automatically control the position of said shoe.

In testimony whereofI afiix my signature. I

' JOSEPH ZUBATY. 2

ment can be had. In a construction which is 7 an aid to easy starting one of the bearings is arranged to rotate together with the driving shaft. When a rotating magnet is used so that it cannot be used to retard undesirable oscillation of the speedcup and where also a rotating spindle bearing is made use of, the indicator is very unsteady. To check such unsteadiness, the structure shown in Figure 6 has been arranged. Bythe adjustment of the cover into or out of the cup, variable pressure is afforded by the cotton within the cup uponv It will be observedthe rotating spindle. that in this figure the magnet and spindle hearing are not shown, also that the structure differs somewhat from that shown in means for preventing the oscillation of the speed cup may readily be applied to the arrangement of Figure 1, with which it is particularly useful in an arrangement as therein shown where the magnet rotates and where one spindle bearing also rotates with the rotary shaft. I

Having described my invention, I claim:

' 1. In a magnetic measuring instrument a casing of magnetic material, a permanent bar magnet, means to vary the efficiency thereof comprlsmg a shoe of magnetic material slidable along an end of said magnet toward and from the casing and heat sensitive means to control the position of said shoe.

2. In a magnetic measuring instrument a casing of magnetic material, a rotor shaft, a permanent bar magnet carriedthereby, a

shoe of magnetic material slidable along an end ofsaid magnet toward and from the cas- Figure 7 1. Itwill be obvious, however, that the ing, heat sensitive means'connected to said I I 7 shoe and mounted upon sald rotor shaft with said magnet.

. 3. In a magnetic measuring instrument, a 

